/***
 * ASM: a very small and fast Java bytecode manipulation framework
 * Copyright (c) 2000-2011 INRIA, France Telecom
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the copyright holders nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */
package com.sinosoft.monitor.org.objectweb.asm;

/**
 * Information about the input and output stack map frames of a basic block.
 *
 * @author Eric Bruneton
 */
final class Frame {

    /*
     * Frames are computed in a two steps process: during the visit of each
     * instruction, the state of the frame at the end of current basic block is
     * updated by simulating the action of the instruction on the previous state
     * of this so called "output frame". In visitMaxs, a fix point algorithm is
     * used to compute the "input frame" of each basic block, i.e. the stack map
     * frame at the beginning of the basic block, starting from the input frame
     * of the first basic block (which is computed from the method descriptor),
     * and by using the previously computed output frames to compute the input
     * state of the other blocks.
     * 
     * All output and input frames are stored as arrays of integers. Reference
     * and array types are represented by an index into a type table (which is
     * not the same as the constant pool of the class, in order to avoid adding
     * unnecessary constants in the pool - not all computed frames will end up
     * being stored in the stack map table). This allows very fast type
     * comparisons.
     * 
     * Output stack map frames are computed relatively to the input frame of the
     * basic block, which is not yet known when output frames are computed. It
     * is therefore necessary to be able to represent abstract types such as
     * "the type at position x in the input frame locals" or "the type at
     * position x from the top of the input frame stack" or even "the type at
     * position x in the input frame, with y more (or less) array dimensions".
     * This explains the rather complicated type format used in output frames.
     * 
     * This format is the following: DIM KIND VALUE (4, 4 and 24 bits). DIM is a
     * signed number of array dimensions (from -8 to 7). KIND is either BASE,
     * LOCAL or STACK. BASE is used for types that are not relative to the input
     * frame. LOCAL is used for types that are relative to the input local
     * variable types. STACK is used for types that are relative to the input
     * stack types. VALUE depends on KIND. For LOCAL types, it is an index in
     * the input local variable types. For STACK types, it is a position
     * relatively to the top of input frame stack. For BASE types, it is either
     * one of the constants defined in FrameVisitor, or for OBJECT and
     * UNINITIALIZED types, a tag and an index in the type table.
     * 
     * Output frames can contain types of any kind and with a positive or
     * negative dimension (and even unassigned types, represented by 0 - which
     * does not correspond to any valid type value). Input frames can only
     * contain BASE types of positive or null dimension. In all cases the type
     * table contains only internal type names (array type descriptors are
     * forbidden - dimensions must be represented through the DIM field).
     * 
     * The LONG and DOUBLE types are always represented by using two slots (LONG
     * + TOP or DOUBLE + TOP), for local variable types as well as in the
     * operand stack. This is necessary to be able to simulate DUPx_y
     * instructions, whose effect would be dependent on the actual type values
     * if types were always represented by a single slot in the stack (and this
     * is not possible, since actual type values are not always known - cf LOCAL
     * and STACK type kinds).
     */

	/**
	 * Mask to get the dimension of a frame type. This dimension is a signed
	 * integer between -8 and 7.
	 */
	static final int DIM = 0xF0000000;

	/**
	 * Constant to be added to a type to get a type with one more dimension.
	 */
	static final int ARRAY_OF = 0x10000000;

	/**
	 * Constant to be added to a type to get a type with one less dimension.
	 */
	static final int ELEMENT_OF = 0xF0000000;

	/**
	 * Mask to get the kind of a frame type.
	 *
	 * @see #BASE
	 * @see #LOCAL
	 * @see #STACK
	 */
	static final int KIND = 0xF000000;

	/**
	 * Flag used for LOCAL and STACK types. Indicates that if this type happens
	 * to be a long or double type (during the computations of input frames),
	 * then it must be set to TOP because the second word of this value has been
	 * reused to store other data in the basic block. Hence the first word no
	 * longer stores a valid long or double value.
	 */
	static final int TOP_IF_LONG_OR_DOUBLE = 0x800000;

	/**
	 * Mask to get the value of a frame type.
	 */
	static final int VALUE = 0x7FFFFF;

	/**
	 * Mask to get the kind of base types.
	 */
	static final int BASE_KIND = 0xFF00000;

	/**
	 * Mask to get the value of base types.
	 */
	static final int BASE_VALUE = 0xFFFFF;

	/**
	 * Kind of the types that are not relative to an input stack map frame.
	 */
	static final int BASE = 0x1000000;

	/**
	 * Base kind of the base reference types. The BASE_VALUE of such types is an
	 * index into the type table.
	 */
	static final int OBJECT = BASE | 0x700000;

	/**
	 * Base kind of the uninitialized base types. The BASE_VALUE of such types
	 * in an index into the type table (the Item at that index contains both an
	 * instruction offset and an internal class name).
	 */
	static final int UNINITIALIZED = BASE | 0x800000;

	/**
	 * Kind of the types that are relative to the local variable types of an
	 * input stack map frame. The value of such types is a local variable index.
	 */
	private static final int LOCAL = 0x2000000;

	/**
	 * Kind of the the types that are relative to the stack of an input stack
	 * map frame. The value of such types is a position relatively to the top of
	 * this stack.
	 */
	private static final int STACK = 0x3000000;

	/**
	 * The TOP type. This is a BASE type.
	 */
	static final int TOP = BASE | 0;

	/**
	 * The BOOLEAN type. This is a BASE type mainly used for array types.
	 */
	static final int BOOLEAN = BASE | 9;

	/**
	 * The BYTE type. This is a BASE type mainly used for array types.
	 */
	static final int BYTE = BASE | 10;

	/**
	 * The CHAR type. This is a BASE type mainly used for array types.
	 */
	static final int CHAR = BASE | 11;

	/**
	 * The SHORT type. This is a BASE type mainly used for array types.
	 */
	static final int SHORT = BASE | 12;

	/**
	 * The INTEGER type. This is a BASE type.
	 */
	static final int INTEGER = BASE | 1;

	/**
	 * The FLOAT type. This is a BASE type.
	 */
	static final int FLOAT = BASE | 2;

	/**
	 * The DOUBLE type. This is a BASE type.
	 */
	static final int DOUBLE = BASE | 3;

	/**
	 * The LONG type. This is a BASE type.
	 */
	static final int LONG = BASE | 4;

	/**
	 * The NULL type. This is a BASE type.
	 */
	static final int NULL = BASE | 5;

	/**
	 * The UNINITIALIZED_THIS type. This is a BASE type.
	 */
	static final int UNINITIALIZED_THIS = BASE | 6;

	/**
	 * The stack size variation corresponding to each JVM instruction. This
	 * stack variation is equal to the size of the values produced by an
	 * instruction, minus the size of the values consumed by this instruction.
	 */
	static final int[] SIZE;

	/**
	 * Computes the stack size variation corresponding to each JVM instruction.
	 */
	static {
		int i;
		int[] b = new int[202];
		String s = "EFFFFFFFFGGFFFGGFFFEEFGFGFEEEEEEEEEEEEEEEEEEEEDEDEDDDDD"
				+ "CDCDEEEEEEEEEEEEEEEEEEEEBABABBBBDCFFFGGGEDCDCDCDCDCDCDCDCD"
				+ "CDCEEEEDDDDDDDCDCDCEFEFDDEEFFDEDEEEBDDBBDDDDDDCCCCCCCCEFED"
				+ "DDCDCDEEEEEEEEEEFEEEEEEDDEEDDEE";
		for (i = 0; i < b.length; ++i) {
			b[i] = s.charAt(i) - 'E';
		}
		SIZE = b;

		// code to generate the above string
		//
		// int NA = 0; // not applicable (unused opcode or variable size opcode)
		//
		// b = new int[] {
		// 0, //NOP, // visitInsn
		// 1, //ACONST_NULL, // -
		// 1, //ICONST_M1, // -
		// 1, //ICONST_0, // -
		// 1, //ICONST_1, // -
		// 1, //ICONST_2, // -
		// 1, //ICONST_3, // -
		// 1, //ICONST_4, // -
		// 1, //ICONST_5, // -
		// 2, //LCONST_0, // -
		// 2, //LCONST_1, // -
		// 1, //FCONST_0, // -
		// 1, //FCONST_1, // -
		// 1, //FCONST_2, // -
		// 2, //DCONST_0, // -
		// 2, //DCONST_1, // -
		// 1, //BIPUSH, // visitIntInsn
		// 1, //SIPUSH, // -
		// 1, //LDC, // visitLdcInsn
		// NA, //LDC_W, // -
		// NA, //LDC2_W, // -
		// 1, //ILOAD, // visitVarInsn
		// 2, //LLOAD, // -
		// 1, //FLOAD, // -
		// 2, //DLOAD, // -
		// 1, //ALOAD, // -
		// NA, //ILOAD_0, // -
		// NA, //ILOAD_1, // -
		// NA, //ILOAD_2, // -
		// NA, //ILOAD_3, // -
		// NA, //LLOAD_0, // -
		// NA, //LLOAD_1, // -
		// NA, //LLOAD_2, // -
		// NA, //LLOAD_3, // -
		// NA, //FLOAD_0, // -
		// NA, //FLOAD_1, // -
		// NA, //FLOAD_2, // -
		// NA, //FLOAD_3, // -
		// NA, //DLOAD_0, // -
		// NA, //DLOAD_1, // -
		// NA, //DLOAD_2, // -
		// NA, //DLOAD_3, // -
		// NA, //ALOAD_0, // -
		// NA, //ALOAD_1, // -
		// NA, //ALOAD_2, // -
		// NA, //ALOAD_3, // -
		// -1, //IALOAD, // visitInsn
		// 0, //LALOAD, // -
		// -1, //FALOAD, // -
		// 0, //DALOAD, // -
		// -1, //AALOAD, // -
		// -1, //BALOAD, // -
		// -1, //CALOAD, // -
		// -1, //SALOAD, // -
		// -1, //ISTORE, // visitVarInsn
		// -2, //LSTORE, // -
		// -1, //FSTORE, // -
		// -2, //DSTORE, // -
		// -1, //ASTORE, // -
		// NA, //ISTORE_0, // -
		// NA, //ISTORE_1, // -
		// NA, //ISTORE_2, // -
		// NA, //ISTORE_3, // -
		// NA, //LSTORE_0, // -
		// NA, //LSTORE_1, // -
		// NA, //LSTORE_2, // -
		// NA, //LSTORE_3, // -
		// NA, //FSTORE_0, // -
		// NA, //FSTORE_1, // -
		// NA, //FSTORE_2, // -
		// NA, //FSTORE_3, // -
		// NA, //DSTORE_0, // -
		// NA, //DSTORE_1, // -
		// NA, //DSTORE_2, // -
		// NA, //DSTORE_3, // -
		// NA, //ASTORE_0, // -
		// NA, //ASTORE_1, // -
		// NA, //ASTORE_2, // -
		// NA, //ASTORE_3, // -
		// -3, //IASTORE, // visitInsn
		// -4, //LASTORE, // -
		// -3, //FASTORE, // -
		// -4, //DASTORE, // -
		// -3, //AASTORE, // -
		// -3, //BASTORE, // -
		// -3, //CASTORE, // -
		// -3, //SASTORE, // -
		// -1, //POP, // -
		// -2, //POP2, // -
		// 1, //DUP, // -
		// 1, //DUP_X1, // -
		// 1, //DUP_X2, // -
		// 2, //DUP2, // -
		// 2, //DUP2_X1, // -
		// 2, //DUP2_X2, // -
		// 0, //SWAP, // -
		// -1, //IADD, // -
		// -2, //LADD, // -
		// -1, //FADD, // -
		// -2, //DADD, // -
		// -1, //ISUB, // -
		// -2, //LSUB, // -
		// -1, //FSUB, // -
		// -2, //DSUB, // -
		// -1, //IMUL, // -
		// -2, //LMUL, // -
		// -1, //FMUL, // -
		// -2, //DMUL, // -
		// -1, //IDIV, // -
		// -2, //LDIV, // -
		// -1, //FDIV, // -
		// -2, //DDIV, // -
		// -1, //IREM, // -
		// -2, //LREM, // -
		// -1, //FREM, // -
		// -2, //DREM, // -
		// 0, //INEG, // -
		// 0, //LNEG, // -
		// 0, //FNEG, // -
		// 0, //DNEG, // -
		// -1, //ISHL, // -
		// -1, //LSHL, // -
		// -1, //ISHR, // -
		// -1, //LSHR, // -
		// -1, //IUSHR, // -
		// -1, //LUSHR, // -
		// -1, //IAND, // -
		// -2, //LAND, // -
		// -1, //IOR, // -
		// -2, //LOR, // -
		// -1, //IXOR, // -
		// -2, //LXOR, // -
		// 0, //IINC, // visitIincInsn
		// 1, //I2L, // visitInsn
		// 0, //I2F, // -
		// 1, //I2D, // -
		// -1, //L2I, // -
		// -1, //L2F, // -
		// 0, //L2D, // -
		// 0, //F2I, // -
		// 1, //F2L, // -
		// 1, //F2D, // -
		// -1, //D2I, // -
		// 0, //D2L, // -
		// -1, //D2F, // -
		// 0, //I2B, // -
		// 0, //I2C, // -
		// 0, //I2S, // -
		// -3, //LCMP, // -
		// -1, //FCMPL, // -
		// -1, //FCMPG, // -
		// -3, //DCMPL, // -
		// -3, //DCMPG, // -
		// -1, //IFEQ, // visitJumpInsn
		// -1, //IFNE, // -
		// -1, //IFLT, // -
		// -1, //IFGE, // -
		// -1, //IFGT, // -
		// -1, //IFLE, // -
		// -2, //IF_ICMPEQ, // -
		// -2, //IF_ICMPNE, // -
		// -2, //IF_ICMPLT, // -
		// -2, //IF_ICMPGE, // -
		// -2, //IF_ICMPGT, // -
		// -2, //IF_ICMPLE, // -
		// -2, //IF_ACMPEQ, // -
		// -2, //IF_ACMPNE, // -
		// 0, //GOTO, // -
		// 1, //JSR, // -
		// 0, //RET, // visitVarInsn
		// -1, //TABLESWITCH, // visiTableSwitchInsn
		// -1, //LOOKUPSWITCH, // visitLookupSwitch
		// -1, //IRETURN, // visitInsn
		// -2, //LRETURN, // -
		// -1, //FRETURN, // -
		// -2, //DRETURN, // -
		// -1, //ARETURN, // -
		// 0, //RETURN, // -
		// NA, //GETSTATIC, // visitFieldInsn
		// NA, //PUTSTATIC, // -
		// NA, //GETFIELD, // -
		// NA, //PUTFIELD, // -
		// NA, //INVOKEVIRTUAL, // visitMethodInsn
		// NA, //INVOKESPECIAL, // -
		// NA, //INVOKESTATIC, // -
		// NA, //INVOKEINTERFACE, // -
		// NA, //INVOKEDYNAMIC, // visitInvokeDynamicInsn
		// 1, //NEW, // visitTypeInsn
		// 0, //NEWARRAY, // visitIntInsn
		// 0, //ANEWARRAY, // visitTypeInsn
		// 0, //ARRAYLENGTH, // visitInsn
		// NA, //ATHROW, // -
		// 0, //CHECKCAST, // visitTypeInsn
		// 0, //INSTANCEOF, // -
		// -1, //MONITORENTER, // visitInsn
		// -1, //MONITOREXIT, // -
		// NA, //WIDE, // NOT VISITED
		// NA, //MULTIANEWARRAY, // visitMultiANewArrayInsn
		// -1, //IFNULL, // visitJumpInsn
		// -1, //IFNONNULL, // -
		// NA, //GOTO_W, // -
		// NA, //JSR_W, // -
		// };
		// for (i = 0; i < b.length; ++i) {
		// System.err.print((char)('E' + b[i]));
		// }
		// System.err.println();
	}

	/**
	 * The label (i.e. basic block) to which these input and output stack map
	 * frames correspond.
	 */
	Label owner;

	/**
	 * The input stack map frame locals.
	 */
	int[] inputLocals;

	/**
	 * The input stack map frame stack.
	 */
	int[] inputStack;

	/**
	 * The output stack map frame locals.
	 */
	private int[] outputLocals;

	/**
	 * The output stack map frame stack.
	 */
	private int[] outputStack;

	/**
	 * Relative size of the output stack. The exact semantics of this field
	 * depends on the algorithm that is used.
	 * <p/>
	 * When only the maximum stack size is computed, this field is the size of
	 * the output stack relatively to the top of the input stack.
	 * <p/>
	 * When the stack map frames are completely computed, this field is the
	 * actual number of types in {@link #outputStack}.
	 */
	private int outputStackTop;

	/**
	 * Number of types that are initialized in the basic block.
	 *
	 * @see #initializations
	 */
	private int initializationCount;

	/**
	 * The types that are initialized in the basic block. A constructor
	 * invocation on an UNINITIALIZED or UNINITIALIZED_THIS type must replace
	 * <i>every occurence</i> of this type in the local variables and in the
	 * operand stack. This cannot be done during the first phase of the
	 * algorithm since, during this phase, the local variables and the operand
	 * stack are not completely computed. It is therefore necessary to store the
	 * types on which constructors are invoked in the basic block, in order to
	 * do this replacement during the second phase of the algorithm, where the
	 * frames are fully computed. Note that this array can contain types that
	 * are relative to input locals or to the input stack (see below for the
	 * description of the algorithm).
	 */
	private int[] initializations;

	/**
	 * Returns the output frame local variable type at the given index.
	 *
	 * @param local the index of the local that must be returned.
	 * @return the output frame local variable type at the given index.
	 */
	private int get(final int local) {
		if (outputLocals == null || local >= outputLocals.length) {
			// this local has never been assigned in this basic block,
			// so it is still equal to its value in the input frame
			return LOCAL | local;
		} else {
			int type = outputLocals[local];
			if (type == 0) {
				// this local has never been assigned in this basic block,
				// so it is still equal to its value in the input frame
				type = outputLocals[local] = LOCAL | local;
			}
			return type;
		}
	}

	/**
	 * Sets the output frame local variable type at the given index.
	 *
	 * @param local the index of the local that must be set.
	 * @param type  the value of the local that must be set.
	 */
	private void set(final int local, final int type) {
		// creates and/or resizes the output local variables array if necessary
		if (outputLocals == null) {
			outputLocals = new int[10];
		}
		int n = outputLocals.length;
		if (local >= n) {
			int[] t = new int[Math.max(local + 1, 2 * n)];
			System.arraycopy(outputLocals, 0, t, 0, n);
			outputLocals = t;
		}
		// sets the local variable
		outputLocals[local] = type;
	}

	/**
	 * Pushes a new type onto the output frame stack.
	 *
	 * @param type the type that must be pushed.
	 */
	private void push(final int type) {
		// creates and/or resizes the output stack array if necessary
		if (outputStack == null) {
			outputStack = new int[10];
		}
		int n = outputStack.length;
		if (outputStackTop >= n) {
			int[] t = new int[Math.max(outputStackTop + 1, 2 * n)];
			System.arraycopy(outputStack, 0, t, 0, n);
			outputStack = t;
		}
		// pushes the type on the output stack
		outputStack[outputStackTop++] = type;
		// updates the maximun height reached by the output stack, if needed
		int top = owner.inputStackTop + outputStackTop;
		if (top > owner.outputStackMax) {
			owner.outputStackMax = top;
		}
	}

	/**
	 * Pushes a new type onto the output frame stack.
	 *
	 * @param cw   the ClassWriter to which this label belongs.
	 * @param desc the descriptor of the type to be pushed. Can also be a method
	 *             descriptor (in this case this method pushes its return type
	 *             onto the output frame stack).
	 */
	private void push(final ClassWriter cw, final String desc) {
		int type = type(cw, desc);
		if (type != 0) {
			push(type);
			if (type == LONG || type == DOUBLE) {
				push(TOP);
			}
		}
	}

	/**
	 * Returns the int encoding of the given type.
	 *
	 * @param cw   the ClassWriter to which this label belongs.
	 * @param desc a type descriptor.
	 * @return the int encoding of the given type.
	 */
	private static int type(final ClassWriter cw, final String desc) {
		String t;
		int index = desc.charAt(0) == '(' ? desc.indexOf(')') + 1 : 0;
		switch (desc.charAt(index)) {
			case 'V':
				return 0;
			case 'Z':
			case 'C':
			case 'B':
			case 'S':
			case 'I':
				return INTEGER;
			case 'F':
				return FLOAT;
			case 'J':
				return LONG;
			case 'D':
				return DOUBLE;
			case 'L':
				// stores the internal name, not the descriptor!
				t = desc.substring(index + 1, desc.length() - 1);
				return OBJECT | cw.addType(t);
			// case '[':
			default:
				// extracts the dimensions and the element type
				int data;
				int dims = index + 1;
				while (desc.charAt(dims) == '[') {
					++dims;
				}
				switch (desc.charAt(dims)) {
					case 'Z':
						data = BOOLEAN;
						break;
					case 'C':
						data = CHAR;
						break;
					case 'B':
						data = BYTE;
						break;
					case 'S':
						data = SHORT;
						break;
					case 'I':
						data = INTEGER;
						break;
					case 'F':
						data = FLOAT;
						break;
					case 'J':
						data = LONG;
						break;
					case 'D':
						data = DOUBLE;
						break;
					// case 'L':
					default:
						// stores the internal name, not the descriptor
						t = desc.substring(dims + 1, desc.length() - 1);
						data = OBJECT | cw.addType(t);
				}
				return (dims - index) << 28 | data;
		}
	}

	/**
	 * Pops a type from the output frame stack and returns its value.
	 *
	 * @return the type that has been popped from the output frame stack.
	 */
	private int pop() {
		if (outputStackTop > 0) {
			return outputStack[--outputStackTop];
		} else {
			// if the output frame stack is empty, pops from the input stack
			return STACK | -(--owner.inputStackTop);
		}
	}

	/**
	 * Pops the given number of types from the output frame stack.
	 *
	 * @param elements the number of types that must be popped.
	 */
	private void pop(final int elements) {
		if (outputStackTop >= elements) {
			outputStackTop -= elements;
		} else {
			// if the number of elements to be popped is greater than the number
			// of elements in the output stack, clear it, and pops the remaining
			// elements from the input stack.
			owner.inputStackTop -= elements - outputStackTop;
			outputStackTop = 0;
		}
	}

	/**
	 * Pops a type from the output frame stack.
	 *
	 * @param desc the descriptor of the type to be popped. Can also be a method
	 *             descriptor (in this case this method pops the types
	 *             corresponding to the method arguments).
	 */
	private void pop(final String desc) {
		char c = desc.charAt(0);
		if (c == '(') {
			pop((Type.getArgumentsAndReturnSizes(desc) >> 2) - 1);
		} else if (c == 'J' || c == 'D') {
			pop(2);
		} else {
			pop(1);
		}
	}

	/**
	 * Adds a new type to the list of types on which a constructor is invoked in
	 * the basic block.
	 *
	 * @param var a type on a which a constructor is invoked.
	 */
	private void init(final int var) {
		// creates and/or resizes the initializations array if necessary
		if (initializations == null) {
			initializations = new int[2];
		}
		int n = initializations.length;
		if (initializationCount >= n) {
			int[] t = new int[Math.max(initializationCount + 1, 2 * n)];
			System.arraycopy(initializations, 0, t, 0, n);
			initializations = t;
		}
		// stores the type to be initialized
		initializations[initializationCount++] = var;
	}

	/**
	 * Replaces the given type with the appropriate type if it is one of the
	 * types on which a constructor is invoked in the basic block.
	 *
	 * @param cw the ClassWriter to which this label belongs.
	 * @param t  a type
	 * @return t or, if t is one of the types on which a constructor is invoked
	 *         in the basic block, the type corresponding to this constructor.
	 */
	private int init(final ClassWriter cw, final int t) {
		int s;
		if (t == UNINITIALIZED_THIS) {
			s = OBJECT | cw.addType(cw.thisName);
		} else if ((t & (DIM | BASE_KIND)) == UNINITIALIZED) {
			String type = cw.typeTable[t & BASE_VALUE].strVal1;
			s = OBJECT | cw.addType(type);
		} else {
			return t;
		}
		for (int j = 0; j < initializationCount; ++j) {
			int u = initializations[j];
			int dim = u & DIM;
			int kind = u & KIND;
			if (kind == LOCAL) {
				u = dim + inputLocals[u & VALUE];
			} else if (kind == STACK) {
				u = dim + inputStack[inputStack.length - (u & VALUE)];
			}
			if (t == u) {
				return s;
			}
		}
		return t;
	}

	/**
	 * Initializes the input frame of the first basic block from the method
	 * descriptor.
	 *
	 * @param cw        the ClassWriter to which this label belongs.
	 * @param access    the access flags of the method to which this label belongs.
	 * @param args      the formal parameter types of this method.
	 * @param maxLocals the maximum number of local variables of this method.
	 */
	void initInputFrame(final ClassWriter cw, final int access,
	                    final Type[] args, final int maxLocals) {
		inputLocals = new int[maxLocals];
		inputStack = new int[0];
		int i = 0;
		if ((access & Opcodes.ACC_STATIC) == 0) {
			if ((access & MethodWriter.ACC_CONSTRUCTOR) == 0) {
				inputLocals[i++] = OBJECT | cw.addType(cw.thisName);
			} else {
				inputLocals[i++] = UNINITIALIZED_THIS;
			}
		}
		for (int j = 0; j < args.length; ++j) {
			int t = type(cw, args[j].getDescriptor());
			inputLocals[i++] = t;
			if (t == LONG || t == DOUBLE) {
				inputLocals[i++] = TOP;
			}
		}
		while (i < maxLocals) {
			inputLocals[i++] = TOP;
		}
	}

	/**
	 * Simulates the action of the given instruction on the output stack frame.
	 *
	 * @param opcode the opcode of the instruction.
	 * @param arg    the operand of the instruction, if any.
	 * @param cw     the class writer to which this label belongs.
	 * @param item   the operand of the instructions, if any.
	 */
	void execute(final int opcode, final int arg, final ClassWriter cw,
	             final Item item) {
		int t1, t2, t3, t4;
		switch (opcode) {
			case Opcodes.NOP:
			case Opcodes.INEG:
			case Opcodes.LNEG:
			case Opcodes.FNEG:
			case Opcodes.DNEG:
			case Opcodes.I2B:
			case Opcodes.I2C:
			case Opcodes.I2S:
			case Opcodes.GOTO:
			case Opcodes.RETURN:
				break;
			case Opcodes.ACONST_NULL:
				push(NULL);
				break;
			case Opcodes.ICONST_M1:
			case Opcodes.ICONST_0:
			case Opcodes.ICONST_1:
			case Opcodes.ICONST_2:
			case Opcodes.ICONST_3:
			case Opcodes.ICONST_4:
			case Opcodes.ICONST_5:
			case Opcodes.BIPUSH:
			case Opcodes.SIPUSH:
			case Opcodes.ILOAD:
				push(INTEGER);
				break;
			case Opcodes.LCONST_0:
			case Opcodes.LCONST_1:
			case Opcodes.LLOAD:
				push(LONG);
				push(TOP);
				break;
			case Opcodes.FCONST_0:
			case Opcodes.FCONST_1:
			case Opcodes.FCONST_2:
			case Opcodes.FLOAD:
				push(FLOAT);
				break;
			case Opcodes.DCONST_0:
			case Opcodes.DCONST_1:
			case Opcodes.DLOAD:
				push(DOUBLE);
				push(TOP);
				break;
			case Opcodes.LDC:
				switch (item.type) {
					case ClassWriter.INT:
						push(INTEGER);
						break;
					case ClassWriter.LONG:
						push(LONG);
						push(TOP);
						break;
					case ClassWriter.FLOAT:
						push(FLOAT);
						break;
					case ClassWriter.DOUBLE:
						push(DOUBLE);
						push(TOP);
						break;
					case ClassWriter.CLASS:
						push(OBJECT | cw.addType("java/lang/Class"));
						break;
					case ClassWriter.STR:
						push(OBJECT | cw.addType("java/lang/String"));
						break;
					case ClassWriter.MTYPE:
						push(OBJECT | cw.addType("java/lang/invoke/MethodType"));
						break;
					// case ClassWriter.HANDLE_BASE + [1..9]:
					default:
						push(OBJECT | cw.addType("java/lang/invoke/MethodHandle"));
				}
				break;
			case Opcodes.ALOAD:
				push(get(arg));
				break;
			case Opcodes.IALOAD:
			case Opcodes.BALOAD:
			case Opcodes.CALOAD:
			case Opcodes.SALOAD:
				pop(2);
				push(INTEGER);
				break;
			case Opcodes.LALOAD:
			case Opcodes.D2L:
				pop(2);
				push(LONG);
				push(TOP);
				break;
			case Opcodes.FALOAD:
				pop(2);
				push(FLOAT);
				break;
			case Opcodes.DALOAD:
			case Opcodes.L2D:
				pop(2);
				push(DOUBLE);
				push(TOP);
				break;
			case Opcodes.AALOAD:
				pop(1);
				t1 = pop();
				push(ELEMENT_OF + t1);
				break;
			case Opcodes.ISTORE:
			case Opcodes.FSTORE:
			case Opcodes.ASTORE:
				t1 = pop();
				set(arg, t1);
				if (arg > 0) {
					t2 = get(arg - 1);
					// if t2 is of kind STACK or LOCAL we cannot know its size!
					if (t2 == LONG || t2 == DOUBLE) {
						set(arg - 1, TOP);
					} else if ((t2 & KIND) != BASE) {
						set(arg - 1, t2 | TOP_IF_LONG_OR_DOUBLE);
					}
				}
				break;
			case Opcodes.LSTORE:
			case Opcodes.DSTORE:
				pop(1);
				t1 = pop();
				set(arg, t1);
				set(arg + 1, TOP);
				if (arg > 0) {
					t2 = get(arg - 1);
					// if t2 is of kind STACK or LOCAL we cannot know its size!
					if (t2 == LONG || t2 == DOUBLE) {
						set(arg - 1, TOP);
					} else if ((t2 & KIND) != BASE) {
						set(arg - 1, t2 | TOP_IF_LONG_OR_DOUBLE);
					}
				}
				break;
			case Opcodes.IASTORE:
			case Opcodes.BASTORE:
			case Opcodes.CASTORE:
			case Opcodes.SASTORE:
			case Opcodes.FASTORE:
			case Opcodes.AASTORE:
				pop(3);
				break;
			case Opcodes.LASTORE:
			case Opcodes.DASTORE:
				pop(4);
				break;
			case Opcodes.POP:
			case Opcodes.IFEQ:
			case Opcodes.IFNE:
			case Opcodes.IFLT:
			case Opcodes.IFGE:
			case Opcodes.IFGT:
			case Opcodes.IFLE:
			case Opcodes.IRETURN:
			case Opcodes.FRETURN:
			case Opcodes.ARETURN:
			case Opcodes.TABLESWITCH:
			case Opcodes.LOOKUPSWITCH:
			case Opcodes.ATHROW:
			case Opcodes.MONITORENTER:
			case Opcodes.MONITOREXIT:
			case Opcodes.IFNULL:
			case Opcodes.IFNONNULL:
				pop(1);
				break;
			case Opcodes.POP2:
			case Opcodes.IF_ICMPEQ:
			case Opcodes.IF_ICMPNE:
			case Opcodes.IF_ICMPLT:
			case Opcodes.IF_ICMPGE:
			case Opcodes.IF_ICMPGT:
			case Opcodes.IF_ICMPLE:
			case Opcodes.IF_ACMPEQ:
			case Opcodes.IF_ACMPNE:
			case Opcodes.LRETURN:
			case Opcodes.DRETURN:
				pop(2);
				break;
			case Opcodes.DUP:
				t1 = pop();
				push(t1);
				push(t1);
				break;
			case Opcodes.DUP_X1:
				t1 = pop();
				t2 = pop();
				push(t1);
				push(t2);
				push(t1);
				break;
			case Opcodes.DUP_X2:
				t1 = pop();
				t2 = pop();
				t3 = pop();
				push(t1);
				push(t3);
				push(t2);
				push(t1);
				break;
			case Opcodes.DUP2:
				t1 = pop();
				t2 = pop();
				push(t2);
				push(t1);
				push(t2);
				push(t1);
				break;
			case Opcodes.DUP2_X1:
				t1 = pop();
				t2 = pop();
				t3 = pop();
				push(t2);
				push(t1);
				push(t3);
				push(t2);
				push(t1);
				break;
			case Opcodes.DUP2_X2:
				t1 = pop();
				t2 = pop();
				t3 = pop();
				t4 = pop();
				push(t2);
				push(t1);
				push(t4);
				push(t3);
				push(t2);
				push(t1);
				break;
			case Opcodes.SWAP:
				t1 = pop();
				t2 = pop();
				push(t1);
				push(t2);
				break;
			case Opcodes.IADD:
			case Opcodes.ISUB:
			case Opcodes.IMUL:
			case Opcodes.IDIV:
			case Opcodes.IREM:
			case Opcodes.IAND:
			case Opcodes.IOR:
			case Opcodes.IXOR:
			case Opcodes.ISHL:
			case Opcodes.ISHR:
			case Opcodes.IUSHR:
			case Opcodes.L2I:
			case Opcodes.D2I:
			case Opcodes.FCMPL:
			case Opcodes.FCMPG:
				pop(2);
				push(INTEGER);
				break;
			case Opcodes.LADD:
			case Opcodes.LSUB:
			case Opcodes.LMUL:
			case Opcodes.LDIV:
			case Opcodes.LREM:
			case Opcodes.LAND:
			case Opcodes.LOR:
			case Opcodes.LXOR:
				pop(4);
				push(LONG);
				push(TOP);
				break;
			case Opcodes.FADD:
			case Opcodes.FSUB:
			case Opcodes.FMUL:
			case Opcodes.FDIV:
			case Opcodes.FREM:
			case Opcodes.L2F:
			case Opcodes.D2F:
				pop(2);
				push(FLOAT);
				break;
			case Opcodes.DADD:
			case Opcodes.DSUB:
			case Opcodes.DMUL:
			case Opcodes.DDIV:
			case Opcodes.DREM:
				pop(4);
				push(DOUBLE);
				push(TOP);
				break;
			case Opcodes.LSHL:
			case Opcodes.LSHR:
			case Opcodes.LUSHR:
				pop(3);
				push(LONG);
				push(TOP);
				break;
			case Opcodes.IINC:
				set(arg, INTEGER);
				break;
			case Opcodes.I2L:
			case Opcodes.F2L:
				pop(1);
				push(LONG);
				push(TOP);
				break;
			case Opcodes.I2F:
				pop(1);
				push(FLOAT);
				break;
			case Opcodes.I2D:
			case Opcodes.F2D:
				pop(1);
				push(DOUBLE);
				push(TOP);
				break;
			case Opcodes.F2I:
			case Opcodes.ARRAYLENGTH:
			case Opcodes.INSTANCEOF:
				pop(1);
				push(INTEGER);
				break;
			case Opcodes.LCMP:
			case Opcodes.DCMPL:
			case Opcodes.DCMPG:
				pop(4);
				push(INTEGER);
				break;
			case Opcodes.JSR:
			case Opcodes.RET:
				throw new RuntimeException(
						"JSR/RET are not supported with computeFrames option");
			case Opcodes.GETSTATIC:
				push(cw, item.strVal3);
				break;
			case Opcodes.PUTSTATIC:
				pop(item.strVal3);
				break;
			case Opcodes.GETFIELD:
				pop(1);
				push(cw, item.strVal3);
				break;
			case Opcodes.PUTFIELD:
				pop(item.strVal3);
				pop();
				break;
			case Opcodes.INVOKEVIRTUAL:
			case Opcodes.INVOKESPECIAL:
			case Opcodes.INVOKESTATIC:
			case Opcodes.INVOKEINTERFACE:
				pop(item.strVal3);
				if (opcode != Opcodes.INVOKESTATIC) {
					t1 = pop();
					if (opcode == Opcodes.INVOKESPECIAL
							&& item.strVal2.charAt(0) == '<') {
						init(t1);
					}
				}
				push(cw, item.strVal3);
				break;
			case Opcodes.INVOKEDYNAMIC:
				pop(item.strVal2);
				push(cw, item.strVal2);
				break;
			case Opcodes.NEW:
				push(UNINITIALIZED | cw.addUninitializedType(item.strVal1, arg));
				break;
			case Opcodes.NEWARRAY:
				pop();
				switch (arg) {
					case Opcodes.T_BOOLEAN:
						push(ARRAY_OF | BOOLEAN);
						break;
					case Opcodes.T_CHAR:
						push(ARRAY_OF | CHAR);
						break;
					case Opcodes.T_BYTE:
						push(ARRAY_OF | BYTE);
						break;
					case Opcodes.T_SHORT:
						push(ARRAY_OF | SHORT);
						break;
					case Opcodes.T_INT:
						push(ARRAY_OF | INTEGER);
						break;
					case Opcodes.T_FLOAT:
						push(ARRAY_OF | FLOAT);
						break;
					case Opcodes.T_DOUBLE:
						push(ARRAY_OF | DOUBLE);
						break;
					// case Opcodes.T_LONG:
					default:
						push(ARRAY_OF | LONG);
						break;
				}
				break;
			case Opcodes.ANEWARRAY:
				String s = item.strVal1;
				pop();
				if (s.charAt(0) == '[') {
					push(cw, '[' + s);
				} else {
					push(ARRAY_OF | OBJECT | cw.addType(s));
				}
				break;
			case Opcodes.CHECKCAST:
				s = item.strVal1;
				pop();
				if (s.charAt(0) == '[') {
					push(cw, s);
				} else {
					push(OBJECT | cw.addType(s));
				}
				break;
			// case Opcodes.MULTIANEWARRAY:
			default:
				pop(arg);
				push(cw, item.strVal1);
				break;
		}
	}

	/**
	 * Merges the input frame of the given basic block with the input and output
	 * frames of this basic block. Returns <tt>true</tt> if the input frame of
	 * the given label has been changed by this operation.
	 *
	 * @param cw    the ClassWriter to which this label belongs.
	 * @param frame the basic block whose input frame must be updated.
	 * @param edge  the kind of the {@link com.sinosoft.monitor.org.objectweb.asm.Edge} between this label and 'label'.
	 *              See {@link com.sinosoft.monitor.org.objectweb.asm.Edge#info}.
	 * @return <tt>true</tt> if the input frame of the given label has been
	 *         changed by this operation.
	 */
	boolean merge(final ClassWriter cw, final Frame frame, final int edge) {
		boolean changed = false;
		int i, s, dim, kind, t;

		int nLocal = inputLocals.length;
		int nStack = inputStack.length;
		if (frame.inputLocals == null) {
			frame.inputLocals = new int[nLocal];
			changed = true;
		}

		for (i = 0; i < nLocal; ++i) {
			if (outputLocals != null && i < outputLocals.length) {
				s = outputLocals[i];
				if (s == 0) {
					t = inputLocals[i];
				} else {
					dim = s & DIM;
					kind = s & KIND;
					if (kind == BASE) {
						t = s;
					} else {
						if (kind == LOCAL) {
							t = dim + inputLocals[s & VALUE];
						} else {
							t = dim + inputStack[nStack - (s & VALUE)];
						}
						if ((s & TOP_IF_LONG_OR_DOUBLE) != 0
								&& (t == LONG || t == DOUBLE)) {
							t = TOP;
						}
					}
				}
			} else {
				t = inputLocals[i];
			}
			if (initializations != null) {
				t = init(cw, t);
			}
			changed |= merge(cw, t, frame.inputLocals, i);
		}

		if (edge > 0) {
			for (i = 0; i < nLocal; ++i) {
				t = inputLocals[i];
				changed |= merge(cw, t, frame.inputLocals, i);
			}
			if (frame.inputStack == null) {
				frame.inputStack = new int[1];
				changed = true;
			}
			changed |= merge(cw, edge, frame.inputStack, 0);
			return changed;
		}

		int nInputStack = inputStack.length + owner.inputStackTop;
		if (frame.inputStack == null) {
			frame.inputStack = new int[nInputStack + outputStackTop];
			changed = true;
		}

		for (i = 0; i < nInputStack; ++i) {
			t = inputStack[i];
			if (initializations != null) {
				t = init(cw, t);
			}
			changed |= merge(cw, t, frame.inputStack, i);
		}
		for (i = 0; i < outputStackTop; ++i) {
			s = outputStack[i];
			dim = s & DIM;
			kind = s & KIND;
			if (kind == BASE) {
				t = s;
			} else {
				if (kind == LOCAL) {
					t = dim + inputLocals[s & VALUE];
				} else {
					t = dim + inputStack[nStack - (s & VALUE)];
				}
				if ((s & TOP_IF_LONG_OR_DOUBLE) != 0
						&& (t == LONG || t == DOUBLE)) {
					t = TOP;
				}
			}
			if (initializations != null) {
				t = init(cw, t);
			}
			changed |= merge(cw, t, frame.inputStack, nInputStack + i);
		}
		return changed;
	}

	/**
	 * Merges the type at the given index in the given type array with the given
	 * type. Returns <tt>true</tt> if the type array has been modified by this
	 * operation.
	 *
	 * @param cw    the ClassWriter to which this label belongs.
	 * @param t     the type with which the type array element must be merged.
	 * @param types an array of types.
	 * @param index the index of the type that must be merged in 'types'.
	 * @return <tt>true</tt> if the type array has been modified by this
	 *         operation.
	 */
	private static boolean merge(final ClassWriter cw, int t,
	                             final int[] types, final int index) {
		int u = types[index];
		if (u == t) {
			// if the types are equal, merge(u,t)=u, so there is no change
			return false;
		}
		if ((t & ~DIM) == NULL) {
			if (u == NULL) {
				return false;
			}
			t = NULL;
		}
		if (u == 0) {
			// if types[index] has never been assigned, merge(u,t)=t
			types[index] = t;
			return true;
		}
		int v;
		if ((u & BASE_KIND) == OBJECT || (u & DIM) != 0) {
			// if u is a reference type of any dimension
			if (t == NULL) {
				// if t is the NULL type, merge(u,t)=u, so there is no change
				return false;
			} else if ((t & (DIM | BASE_KIND)) == (u & (DIM | BASE_KIND))) {
				if ((u & BASE_KIND) == OBJECT) {
					// if t is also a reference type, and if u and t have the
					// same dimension merge(u,t) = dim(t) | common parent of the
					// element types of u and t
					v = (t & DIM) | OBJECT
							| cw.getMergedType(t & BASE_VALUE, u & BASE_VALUE);
				} else {
					// if u and t are array types, but not with the same element
					// type, merge(u,t)=java/lang/Object
					v = OBJECT | cw.addType("java/lang/Object");
				}
			} else if ((t & BASE_KIND) == OBJECT || (t & DIM) != 0) {
				// if t is any other reference or array type,
				// merge(u,t)=java/lang/Object
				v = OBJECT | cw.addType("java/lang/Object");
			} else {
				// if t is any other type, merge(u,t)=TOP
				v = TOP;
			}
		} else if (u == NULL) {
			// if u is the NULL type, merge(u,t)=t,
			// or TOP if t is not a reference type
			v = (t & BASE_KIND) == OBJECT || (t & DIM) != 0 ? t : TOP;
		} else {
			// if u is any other type, merge(u,t)=TOP whatever t
			v = TOP;
		}
		if (u != v) {
			types[index] = v;
			return true;
		}
		return false;
	}
}
